The invention relates to product sortation conveyors of the general type taught, for example, in U.S. Pat. No. 4,711,341. Briefly, a product sortation conveyor comprises a frame defining a main line of the conveyor together with one or more branch outlets extending laterally therefrom along one or both sides thereof.
An endless conveying surface or apron is supported for movement on the frame and is characterized by a top conveying flight or run and a bottom return flight or run. The apron comprises a pair of endless roller chains, selected links of which are joined together by transversely extending cross tubes arranged in parallel spaced relationship. A plurality of pusher elements are provided, each pusher element mounted on a pair of adjacent cross tubes throughout the length of the apron. As a consequence, the number of pusher elements on the apron is equal to one-half the number of cross tubes making up the continuous apron. Each pusher element not only travels with the apron in the general conveying direction, but also is adapted for sliding movement across the apron from one side thereof to the other. Means are further provided for causing a desired number of pusher elements to move across the apron as they move forwardly with it, to push a selected product from the apron onto a selected branch outlet.
Sortation conveyors of the type just described can be used with many types of products and packages. They are capable of faultless sortation and can be operated at relatively high rates of speed. Such sortation conveyors are provided with numerous safety devices to assure proper operation and to shut down the conveyor before damage thereto or to the products thereon, should a problem arise.
Sortation problems have been encountered, however, when such conveyors carry Products or packages characterized by high-friction surfaces. Rubber vehicular tires constitute a prime example of products with high-friction surfaces.
In the conveying of rubber vehicular tires on a sortation conveyor of the type taught in U.S. Pat. No. 4,711,341, it was found that the high-friction surfaces of the tires when pushed along the steel cross tubes during a diverting operation caused the tires to chatter or bounce while being diverted by the pusher elements. This chatter effect was so great that approximately one out of ten tires would bounce its way over the pusher element and would not properly divert. Those tires that did divert, appeared to be partially resting on top of the pusher elements and chattered throughout the diverting operation.
When the tires were introduced to the sortation conveyor directly from their molds, so that the side walls of the tires were at an elevated temperature of from about 85.degree. F. to about 135.degree. F. and were very clean, the chatter effect was augmented. Furthermore, the tires being relatively soft, were easily distorted and some became pinched between the pusher elements and their respective cross tubes. Yet another problem was the accumulation of foreign material on the cross tubes, such as rubber flashings, which would interfere with the smooth movement of the pusher elements along their respective cross tubes.
The present invention is based upon the discovery that, with appropriate modifications to the cross tubes and pusher elements, the above-noted problems can be eliminated and products with high-friction surfaces can be properly processed on a sortation conveyor and diverted to one or more branch outlets, as desired.
To this end, the pusher element cap (i.e., that part of each pusher element that contacts the product) was completely redesigned with respect to contour with its height approximately doubled. That surface of the pusher element cap which contacts the tire is inclined upwardly and rearwardly with respect to the direction of diverting and designed to provide a larger contact area to prevent excessive deflection of the tire. The inclined surface applies a lifting force, as well as a horizontal force, to the tire, thereby reducing the weight on the cross tubes which, in turn, reduces the sliding friction forces. The inclined contour also provides a downward force, generated by the tire itself, to hold the pusher element tightly against its respective cross tubes, eliminating the tendency of the higher or taller contour to lift the cross tubes out of their normal operating position. The pusher elements inclined operating surface extends to a position below the uppermost surface of the cross tubes, which is below the conveying surface of the tire. This, in conjunction with the larger contacting surface, minimize deflection, eliminating pinching or binding effects of the tire between the pusher element and its respective cross tubes. The improved pusher elements also enable the sorting of products with a high center of gravity.
In conjunction with the improved pusher elements, the cross tubes of the present invention are coated with a low-friction material having excellent release characteristics and precluding the adhesion of foreign matter on the surfaces of the cross tubes. The frictional forces between the tire and the cross tubes are greatly reduced providing positive sort capabilities for high-friction products. The coating eliminates marking of the tire, such as scratches, as the tire slides on the cross tubes. The coating also renders the cross tubes resistant to corrosion. Chattering or bouncing of the tires during a diverting operation is substantially reduced or eliminated. The steel of the cross tubes provides strength and rigidity, while the coating thereon provides low-friction.